The present invention relates to suspension systems with shock absorbers for vehicles, such as bicycles and motorcycles, and more particularly, to a shock absorber with internal valves to selectively control the damping characteristics of the shock absorber.
Suspension systems have improved the performance and comfort of mountain bicycles. Over rough terrain the suspension system can improve traction and handling by keeping the wheels on the ground. A rider can more easily maintain control at higher speeds and with less effort when the suspension absorbs some of the shock encountered when riding. Ideally, the suspension should react well to both (1) low amplitude, high frequency bumps and (2) high amplitude, low frequency bumps. However, these can be competing requirements for the damping systems in conventional shock absorbers. The suspension system should also provide effective power transfer from the rider to the wheels while in a wide range of riding conditions, including climbing or sprinting.
Higher rebound damping is desirable for high amplitude, low frequency bumps rather than for low amplitude, high frequency bumps. With high frequency, low amplitude bumps, such as may be encountered on a washboard gravel road, minimal damping may be preferable so the shock absorber can quickly recover from a minor impact before the next is encountered. However, with a large bump (such as the size of a curb or a large pot-hole), increased rebound damping aids the rider by keeping the bike from forcefully springing back too quickly, causing loss of traction and control on the rebound.
Some current shock absorbers that include springs and dampers allow the rider to adjust rebound and/or compression damping before a ride. Other air shock absorbers include an on/off switch to disable the shock absorber all together. However, such preadjustment is at best a compromise; the rider must select better damping in one scenario at the expense of the other. A typical off-road mountain bike ride will include small, medium, and large bumps, as well as possibly jumps, drop-offs, and tight descending-to-ascending transitions. If the rider significantly reduces the damping to ride smoothly over high frequency, low amplitude bumps, then the bike may lose traction and control when a large bump is encountered or may xe2x80x9cbottom outxe2x80x9d the shock absorber. If the rider increases the damping force of the shock absorber, then the system will not recover fast enough to quickly absorb high frequency bumps. Also, the rider likely will be rattled and the bike will lose traction.
Another limitation of many current shock absorbers is evidenced by rider-induced bobbing: suspension movement caused by rider movement during pedaling. Related to this is pedal-induced suspension action: the cyclic forces on the chain pulling the rear swing arm up or down relative to the frame. If the damping in the shock absorber is greater, these influences will not be felt as much by the rider, but the bike""s drive line efficiency may be reduced.
Attempts to achieve the competing requirements for a shock absorber include active bypass damping systems. These systems regulate the bypass flow of damping fluid through the damper depending upon the velocity and displacement of the damper""s piston relative to the damper body. Such active bypass damping systems are described in detail in co-pending U.S. patent application Ser. Nos. 08/970,820; 08/891,528; and 08/857,125, all of which are hereby incorporated in their entireties herein by reference. These shock absorbers with active bypass damping provide a significant improvement to the shock absorber technology, although the variable damping characteristics are predetermined upon manufacturing, so the rider can not manually adjust the damping characteristics as desired while riding.
Another improved shock absorber is described in detail in co-pending U.S. patent application Ser. No. 09/152,137. This shock absorber provides a variable bypass damping by regulating the flow of damping fluid depending on the velocity and displacement of the shock absorber piston. The variable bypass damping is achieved by mechanical valves that control the bypass flow of fluid relative to the piston depending upon where the piston is during a piston stroke and how fast the piston is moving relative to the piston body. application Ser. No. 09/152,137 is hereby incorporated herein in its entirety by reference. This shock absorber with variable bypass damping provides a significant improvement in the shock absorber art and it utilizes durable, inexpensive mechanical valves for regulation of the damping fluid flow. The shock absorber is pretuned upon manufacturing, however, so it is not manually adjustable by the rider while riding over various terrain conditions. Thus, the rider is not able to manually adjust the stiffness or suppleness of the suspension system while riding.
Suspension systems that react well to both high frequency low amplitude bumps and low frequency/high amplitude bumps provide increased control and traction for the rider because the wheels remain in contact with the ground. While suspension systems are effective at absorbing energy when encountering bumps, the suspension systems also absorb energy from the rider, such as when the rider is pedaling hard while climbing or sprinting. Such absorption of the rider""s energy decreases the efficiency of power transfer from the rider to the ground. Accordingly, suspended bikes provide good control for the rider. Unsuspended bicycles, known as stiff tail bikes, have very efficient power transfer from the rider, but provide less control for the rider. Effective suspension systems, thus, should provide a wide range of suspension action for control, while being able to provide efficient power transfer from the rider, particularly when needed for climbing or sprinting.
When riding a bicycle with a suspension system, it is desirable to have a high performance shock absorber that dampens riding loads while also allowing for highly efficient power transfer from the rider, such as when climbing or sprinting. The action of rear suspension systems can sometimes reduce the efficiency of power transfer from the rider to the ground. The present invention addresses the suspension challenges experienced by the prior art and solves drawbacks experienced by the prior art in selectively accommodating high frequency/low amplitude bumps, low frequency/high amplitude bumps, and rider induced suspension action. The present invention also provides a suspension that is manually adjustable to significantly stiffen the suspension system for increased drive line efficiency. The present invention can be applied to most suspension configurations as it addresses the challenges with a unique adjustable and active damping shock absorber.
The shock absorber includes a lock-out valve that can be adjusted by the rider during use to effectively absorb large bumps, small bumps, and rider-induced suspension bounce, while being activatable to lock out the shock absorber and stiffen the suspension system when needed for increased power efficiency. The shock absorber provides for high performance shock absorption by manual activation of the lock-out valve to create a significantly higher shock compression force, thereby effectively locking shock travel when desired, for example, to increase the bike""s drive line efficiency while climbing or sprinting. The shock absorber also includes a blow-off valve with tuned damping characteristics for two-stage flow restriction in the shock absorber.
The shock absorber includes a damper having a chamber containing a substantially non-compressible fluid, and a piston in the chamber that divides the chamber into first and second portions. The piston is movable relative to the chamber while sealably engaging the chamber. The piston has a primary bypass channel in fluid communication with the chamber""s first and second portions to allow the non-compressible fluid to selectively move between the chamber""s first and second portions when the piston moves relative to the chamber. The lock-out valve is coupled to the bypass channel and is manually moveable from an open position to a closed position. In the closed position, the fluid is blocked from flowing through the primary bypass channel, thereby providing a first damping characteristic of the damper. In the open position, the fluid can flow through the primary bypass channel, thereby providing a second damping characteristic of the damper. Accordingly, the manually activatable lock-out valve allows a rider to actively adjust the damping characteristics of the damper while riding.
In one embodiment, the damper has a manually adjustable actuator connected to the lock-out valve. The actuator is moveable by the rider to cause the lock-out valve to move from the open position to the closed position. The non-compressible fluid is pressurized and acts on the lock-out valve to move it back to the open position when the actuator is released.
In one embodiment, the shock absorber has compression flow channels in fluid communication with the chamber""s first and second portions. A flow regulating valve or blow-off valve is positioned adjacent to the compression flow channels . The blow-off valve is moveable relative to the compression flow channels between closed and open positions. In the closed position, the blow-off valve prevents the non-compressible fluid from flowing through the compression flow channels to the chamber""s second portion. Thus, the damper has stiffened characteristics when the blow-off valve is in the closed position. In the open position, the blow-off valve is spaced away from the compression flow channels and allows the non-compressible fluid to flow through the compression flow channels to the chamber""s second portion. Thus, the damper has a softened characteristic when the blow-off valve is in the open position.
In one embodiment the compression flow channels extend through the piston, and the blow-off valve is adjacent to the piston. The blow-off valve provides a two-stage flow restriction through the piston. The blow-off valve is configured to resist piston motion caused by rider pedaling forces, yet allow piston motion when the suspension system is subjected to larger bump forces sufficient to force the blow-off valve open. The blow-off valve is pre-loaded toward the closed position by a biasing member, The biasing member holds the blow-off valve in the closed position and resists rider-induced forces, such as from pedaling action, until the fluid""s pressure reaches a critical pressure that overcomes the pre-loading of the biasing member. At or above the critical pressure, the non-compressible fluid moves the blow-off valve from the closed position to the open position and flows through the compression flow channels.
The blow-off valve is sized to be spaced slightly apart from the side walls of the chamber to provide a small annulus through which the non-compressible fluid flows when the blow-off valve is in the open position. The blow-off valve provides a large surface area against which the hydraulic fluid can press to hold the blow-off valve in the open position. The small annulus provides a reduced flow passageway past the blow-off valve when in the open position for smooth fluid flow and smooth pressure release that prevents pressure equilibrium from occurring too quickly. Thus, the blow-off valve enables the damper to maintain a supple damping characteristic as the blow-off valve moves between the open and closed positions.
In one embodiment of the invention, the shock absorber is incorporated in a suspension system having first and second vehicle structures moveable relative to each other. The shock absorber""s first chamber is coupled to the first vehicle structure, and the second chamber is coupled to the second vehicle structure. The second chamber has a compressible member therein that provides a biasing force in the shock absorber. The first chamber is slidably disposed in the second chamber and is moveable relative to the second chamber when the first vehicle structure moves relative to the second vehicle structure. Movement of the first chamber into the second chamber compresses the compressible member to increase the biasing force. The shock absorber has a piston assembly moveable relative to the first chamber as the first and second chambers move relative to each other. In one embodiment, the piston includes the manually activatable lock-out valve and the blow-off valve. The suspension system provides for an adjustable damping characteristics to stiffen or soften the shock absorber""s damping characteristics during use as desired by the user.